For the purpose of transmitting as large a quantity of data as possible via an optical waveguide, it is known in optical telecommunications to multiplex the data to be transmitted. One possibility for this purpose is to transmit information independently and simultaneously over one waveguide with the aid of several wavelengths (wavelength division multiplexing—WDM). It is necessary in this case to keep reliably on the transmission side to the various prescribed optical wavelength channels. Thus, there is a need in the transmission modules for an optical arrangement with the aid of which the wavelength of the individual transmission devices can be monitored and, if required, corrected. The aim in this case is for the technical solution provided to be of small overall size, to require little electric power and to be capable of cost effective production.
WO 03/069744 A1 discloses an optoelectronic module in which a laser chip is arranged on a submount and is cooled by a Peltier cooler of small design. Located on the submount for the purpose of monitoring the wavelength emitted by the laser chip is a temperature sensor via which the operating temperature of the laser can be detected. The signal generated by the temperature sensor is fed to an electronic monitoring and control unit via which the temperature is set after a calibration operation on the laser and is kept stable by suitable control of the current by the Peltier cooler. A temperature is set in this case at which the laser emits the desired optical wavelength, which corresponds to a specific WDM channel.
It is also known for the emitted wavelength to be detected directly in order to monitor and control the wavelength of the light emitted by the laser. Use is made for this purpose of relatively complicated optics having one or more wavelength-dependent filters. By directly detecting the emitted wavelength of the laser component, it is possible to achieve a substantially finer stabilization of the wavelength than by exerting control through using a temperature sensor.
The Peltier cooler used in known optoelectronic arrangements for temperature stabilization are disadvantageously relatively large as a rule. Furthermore, they require a relatively large electric power and are comparatively expensive. Optoelectronic modules with wavelength stabilization are therefore cost intensive both to produce and to operate.